Trumpets and air filter advice needed for 40IDFs

[Kerem Ustunkaya]

Dear Friends,
It has been a while since my last post. I hope all is going well in everyone’s life.
I have tried to search for the subject with the weber,idf,trumpets etc keyword but probably I am doing something wrong and my search is not producing any results.

As I mentioned in the topic subject, I need your help for the best trumpet lenght and air filter set up on the 40IDFs. ( 28mm chokes 125 F11 200)
Currently, the 86mm cylinder and piston kit 356C ( Wenzel 200.5 camshaft ) engine has approx. 40mm alloy trumpets in the typical 83mm height KN filters but this combination gave me a great difficulty of reducing the overall richness during the carburetor tuning.
Strange enough, once the KN is removed and only the trumpets left on the IDFs, the car is transformed and became a way easier to tune and the engine responded to every single main and ac jet change in the correct direction.
Then I also tried KN only ( without trumpets ), this also worked well but I must say, trumpet only ( no air filter ) was still better.
When the KN and the trumpet is there, there is a strong black smoke and richness smell visually confirmed from the car behind even during the light but steady acceleration and also at WOT.
So, certainly the trumpet and the KNs are producing a strong richness.
I would very much appreciate if you could advice the best trumpet and air filter combination for road use. ( may be no trumpets at all ?? )
Last but not least, I have read somewhere that the trumpet’s air entry point should have a certain distance from the filter’s base plate ( not the top plate ). If I understood correct, this statement requires a kind of spacer to raise the height of the base plate but I am not sure I understood correct. Regarding the trumpet’s proximity to the top plate of the KNs, what I know is there must be at least 25mm clearance for a better flow and greater the clearance better the result is but nothing to do with the air filter’s base plate as far as the trumpet’s performance concerned.
Best regards,
Kerem

[C J Murray]

It sounds like the oil on your filters is too thick. Get a K&N service kit with cleaner and oil and follow the instructions. If you can't get the kit then you can soak the filters with Gunk engine degreaser and rinse them out with water...then shake them dry and install them without oil. If that makes the mixture more lean then your filters were clogged with heavy oil and/or dirt. K&N air filters correctly serviced should have almost zero effect on jetting or power.

The best velocity stacks that I have found are the stacks that come with new Webers. This link says aluminum but I think they are steel....
http://www.carburetion.com/Products/Pro ... =52845.525

[Phil Planck]

Recent thread that may help

viewtopic.php?f=1&t=45862

[Kerem Ustunkaya]

It sounds like the oil on your filters is too thick. Get a K&N service kit with cleaner and oil and follow the instructions. If you can't get the kit then you can soak the filters with Gunk engine degreaser and rinse them out with water...then shake them dry and install them without oil. If that makes the mixture more lean then your filters were clogged with heavy oil and/or dirt. K&N air filters correctly serviced should have almost zero effect on jetting or power.

The best velocity stacks that I have found are the stacks that come with new Webers. This link says aluminum but I think they are steel....
http://www.carburetion.com/Products/Pro ... =52845.525

Many thanks!!
Just searched, KN cleaner kit is available over here. I will clean them and fit them with the existing VSs first and see how it works.
Regarding the VSs on the link, they are 68mm and the KN filter’s internal height is 86mm, leaving only 18mm to breath. I think the 18mm clearance is little too less than the ideal. Don’t you think so ?
By the way, I normally always prefer the original Weber steel VS as in the link on DCOEs but I am not sure if that 68mm height will work here.

[Kerem Ustunkaya]

Recent thread that may help

viewtopic.php?f=1&t=45862

Thank you very much for the thread link!! That is exactly the velocity stacks under our 86mm KN filter which is the same in that thread as well.
I will ask the poster if they were able to tune that engine without any over richness issues.

[C J Murray]

My 8000rpm race engine uses those stacks inside short K&Ns. There was no difference in power with the tops off of the air cleaners on a dyno. Most of the air entering the stacks does not come from directly above.

[Kerem Ustunkaya]

My 8000rpm race engine uses those stacks inside short K&Ns. There was no difference in power with the tops off of the air cleaners on a dyno. Most of the air entering the stacks does not come from directly above.

IMG_1754.jpg

Hi Murray,
Many thanks for the technical info. After cleaning the K&Ns, I am going to try various stacks to see how they behave in our more or less standard engine. I dont have the 68mm in stock but I will soon get them and try.
Usually longer the stacks better torque in the mid range but as each engine behaves differently, we will see.
By the way, you have a beautiful race engine there with the 8000rpm !!!
Many thanks once more.
Best regards

[Dave Wildrick]

It sounds like the oil on your filters is too thick. Get a K&N service kit with cleaner and oil and follow the instructions. If you can't get the kit then you can soak the filters with Gunk engine degreaser and rinse them out with water...then shake them dry and install them without oil. If that makes the mixture more lean then your filters were clogged with heavy oil and/or dirt. K&N air filters correctly serviced should have almost zero effect on jetting or power.

The best velocity stacks that I have found are the stacks that come with new Webers. This link says aluminum but I think they are steel....
http://www.carburetion.com/Products/Pro ... =52845.525

I believe I recall Craig Richter of this talk list and author of "How to Make an Old Porsche Fly" saying not to use the oil on the K&N filters with Weber IDF40s.

Unrelated to the filter oil issue, I bought aluminum velocity stacks from CB Performance some years ago, and they melted ten years ago when I had a carburetor fire in a Weber IDF40. So, I don't use aluminum stacks anymore.

[C J Murray]

I believe I recall Craig Richter of this talk list and author of "How to Make an Old Porsche Fly" saying not to use the oil on the K&N filters with Weber IDF40s.

For sure you don't want to use thick oil. No oil would be much better than that. The K&N oil is a very light spray.

[Tim Berardelli]

I clean K&N and other gauze filters with a 50/50 mix of Simple Green and hot water.

[Mike Smith]

For sure you don't want to use thick oil. No oil would be much better than that. The K&N oil is a very light spray.

Cliff - our experience is NO Oil is asking for a Fire !

We always advise - `Buy the kit and Oil them`

[C J Murray]

For sure you don't want to use thick oil. No oil would be much better than that. The K&N oil is a very light spray.

Cliff - our experience is NO Oil is asking for a Fire !

We always advise - `Buy the kit and Oil them`

That makes sense.

[Craig Richter]

I've never had a carb fire, but it must be a terrible experience. A '54 Coupe came to Jack's shop a few years ago, burnt to the ground from a carb fire. Nicknamed her "Bernie". Very expensive re-do.
It's easy to see how that K&N mesh could absorb gas and become a bomb, and some oil would lessen that chance. I advised no oil because the air cleaners most used on Webers are kinda small and can clog up quickly with too much or too thick oil. You will notice ratty running when that happens! After hearing stories like Dave's, I used to check Speedy's K&N mesh often for gas saturation, but never found any. There is a larger K&N model air cleaner that fits and doesn't clog as easily. Carry a fire extinguisher!